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What Marc said or...

Here's a quick guide to exhaust sizes to your power out put, thanks to R31Nismoid on SAU here.

300 kW's = 3" exhaust

350 kW's = 3.5" exhaust

400 kW's = 4" exhaust

Your car will be fine with a 3" exhaust.

thats what i was thinking...but a guy told me you need back pressure for a stock turbo ?

people often try and use physics from NA cars on turbo cars, and it doesn't work.

and technically speaking, back pressure is a bad thing on any car. it is just an unwanted byproduct of having an exhaust the right size to maintain the scavenging effect on a NA car.

car is no where stock just the turbo is stock

And if the turbo is stock - there is no way you are making more than 200rwkw :)

turbo is the limiting factor, they don't make over that - end of story.

Apart from the noise a 4" gives, it won't hurt the car as such.

You don't need backpressure, it's a turbo. Whoever is giving such advice, make sure you don't take your car back there. If it's the same guy who's lying to you telling you that the car has 230rwkw, well that just backs the point even more :thumbsup:

BIGGER the better !!!

Turbo works by feeding exhaust gasses to turbo wheel / turning cold side wheel ..... any back pressure would only slow the gasses or wheel down ! .... AND WE DON`T WANT THAT DO WE ;)

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